This application claims the priority of German application 199 39 264.1, filed Aug. 19, 1999, the disclosure of which is expressly incorporated by reference herein.
The present invention relates to a plate heat exchanger, in particular an oil cooler for internal combustion engines, having several identical plates formed as dishes which are stacked on one another, each turned by 180xc2x0, with their edges adjacent to one another and provided with projecting conduits for the formation of feeding and drainage channels for the heat exchange media.
Plate heat exchangers of this type are known from German publication DE 196 54 365 A1. In such heat exchangers, each of the conduits projecting toward one side consists of a collar projecting perpendicularly from one of the plate surfaces. A free edge of the collar is bent inwards and forms an encircling annular surface which, on stacking of the plates on one another, is adjacent to the edge of an opening disposed in the surface of the neighboring plate. Since the plates are subsequently soldered to one another, there arises in this way a passage channel for one of the heat exchange media which is sealed off from the chamber formed between neighboring plates. However, since the diameter of the encircling collar is greater than the diameter of the opening in the neighboring plates by the thickness of the annular surface formed by the edge bent inwards, the heat exchange surface becomes smaller by this annular surface in the chamber separated from the through-flow conduits. The heat exchange is thus not fully utilized.
It has been found that the soldering between the edge of the collar and the surface of the plate sometimes leaves something to be desired since failures of sealing can arise here.
U.S. Pat. No. 5,794,691 discloses that, for increasing the strength of heat exchangers consisting of dishes set on one another, it is possible to provide connecting tongues bent inwards in the area of each passage channel. The connecting tongues can be connected to one another by their edges and thereby contribute to an increase in stability in the area of the passage. In this configuration, for the formation of the passage channels, conduits projecting toward one side, which are adjacent to one another with annular surfaces, are also provided. This configuration, therefore, suffers from the disadvantage that the heat exchange surface available within the chamber is reduced by the formation of the conduits.
Finally, from German publication DE 197 22 074 A1, it is known, in the case of a plate heat exchanger with heat exchanger plates stacked on one another, to form conically tapering collars projecting out from the surface of the plate for the disposition of fastening elements. The collars, like the outer edges of the individual plates, fit into one another and are soldered so that, in this way, supporting sleeves are formed for the fastening of head bolts to be implemented. In this mode of construction, the passage openings for the heat exchange media are formed according to known practices and the heat exchange surface is reduced, in addition, by the supporting passages for the head bolt.
It is one object of the present invention to form a plate heat exchanger of the type mentioned initially so that the heat exchange surface is enlarged in a simple way and the stability of the entire structure is increased.
This object is achieved by providing, in a plate heat exchanger of the type mentioned initially, at least one conduit that projects in the form of a collar conically expanding toward one side of the surface of the plate and a collar conically tapering toward the opposite side of each plate, disposing the collars on the surface of the plate so that they are aligned to one another after a 180xc2x0 turn in the plane of the plate, and coordinating their conicity to one another so that they engage in one another at least partially.
By this configuration, the previous simple type of plate heat exchanger structure made by stacking plates on one another can be retained. Since now, however, the collars provided for the formation of the passage openings project toward different sides, they can engage directly in one another when they are put together so that the disposition of annular soldering surfaces bent outwards is superfluous. The surface available for heat exchange within the chambers is thus enlarged. Furthermore, favorable prerequisites for soldering are created.
According to one feature of the invention, four collars are provided. Two of these collars, identically formed, are disposed symmetrically to a longitudinal plane of each plate so that feeding and drainage of the two media participating in the heat exchange in adjacent chambers within the individual plates is made possible. It has, moreover, been shown that it is very advantageous if the conical angle of the collar is positioned to about 8xc2x0 or 9xc2x0. This permits a simple stacking on one another and a tight fit of the collars before soldering.
According to another feature of the invention, the plates can be provided with encircling edges which project toward one side and at least partially reach over the edge of the neighboring plate.
According to yet another feature of the invention, the collars can engage in openings of turbulence inserts which are mounted between each pair of neighboring plates. Here, the openings in the turbulence inserts can be provided with smaller diameters than in the case of plate heat exchangers according to the state of the art. The heat exchange can thus be improved.
Finally, according to yet another feature of the invention, the collars can disposed as near as possible to the edges bordering the narrow sides of the plates. Since the through-flow of the chambers is done from one passage channel to the passage channel lying opposite in the longitudinal direction of the plate and only a negligible part of the flow is done in the area between the outer edge and the collar, the yield of heat exchange can also be improved in this way.
The invention is represented by way of an exemplary embodiment in the drawings and will now be explained.